[Al Skierkiewicz]

Frank,
All of these breakers, the main included, can withstand several seconds of 600% overload without trip. It is the sustained current over rated current that trips the mechanism. The auto reset limits current in a fashion as the reset features restores current flow rather quickly. In a sustained over current situation these may actually "buzz" as they open and close rapidly. This in effect limits current by changing the average current passing to the load. Not what I would call predictable or effective current limit.